Mike Hillyard, one of the volunteers who rebuilt a replica of the Turing Bombe machine that played a crucial part in cracking the Nazi Enigma Code, stands by the machine at Bletchley Park in Milton Keynes, England, Tuesday, March 24, 2009. The original machine was destroyed after the war but volunteers rebuilt the replica that received a special Engineering Heritage Award on Tuesday to mark its place in history. (AP Photo/Akira Suemori)

Photo: Akira Suemori, ASSOCIATED PRESS

Mike Hillyard, one of the volunteers who rebuilt a replica of the...

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FILE -- This is a Tuesday, June 25, 2002 file picture, showing a four-rotor Enigma machine, right, once used by the crews of German U-boats in World War II to send coded messages, which British World War II code-breaker mathematician Alan Turing, was instrumental in breaking, and which is widely thought to have been a turning point in the war. Homosexuality was illegal in Britain at that time and Alan Turing received medical treatment following his conviction for what was considered indecency, however British Prime Minister Gordon Brown has apologized for the "inhumane" treatment which was metred out to Turing, in a published apology Friday Sept. 11, 2009. (AP Photo/Alex Dorgan Ross)

Alan Turing's was a once-in-a-generation mind, ticking with mathematical insights that helped end a war and usher in the computing era. That uncanny brain, however, wasn't enough to save him from the cruel prejudices of his day.

In fact, rarely has a figure so brilliant and tragic lived outside of novels.

Saturday marked Turing's 100th birthday. But the British war hero and godfather of computer science died at the age of 41, in an apparent suicide following his criminal conviction for sleeping with a man. It's impossible to know just what the world lost through his untimely death, though the toll was assuredly profound.

"He was an astonishingly deep, philosophical thinker, but had the ability to design very pragmatic systems," said Vint Cerf, Google's chief Internet evangelist and one of the original architects of the Internet. "This was a tragedy of monumental proportions."

In 1936, as a prodigious mathematician at the age of 23, Turing published a paper that laid out the basic framework of the modern computer. It was a byproduct of an altogether different goal, a theoretical tool for tackling - technically reformulating - a long-standing puzzle of mathematics known as the Entscheidungsproblem.

"The Entscheidungsproblem might be described as the quest for a sort of ur-algorithm, one by means of which the validity or provability of any argument can be determined," explains David Leavitt in "The Man Who Knew Too Much: Alan Turing and the Invention of the Computer."

Turing proved the problem could not be solved (through means that befuddle this journalism major) - but what concerns us here is the so called Turing Machine he described in the process.

It was supplied with an infinite roll of tape on which it could read, write, remember and erase an endless series of ones and zeros, processing the binary digits in various ways depending on the instructions - or "configuration" - the machine was set to at any given time.

Here then we see fundamental concepts of computing emerging: binary notation, read-write memory and software. The main thing missing in early hardware computers was the infinite tape, which would have to wait for the advent of the Internet.

"Alan Turing gave us a mathematical model of digital computing that has completely withstood the test of time," said George Dyson, author of the new book "Turing's Cathedral." "He gave us a very, very clear description that was truly prophetic."

The bombe

Turing had no intention of building the machine - and might not have even fully grasped the importance of what he had done. But with the onset of World War II, his theoretical work soon took on life-or-death dimensions.

At the now famed Bletchley Park in Buckinghamshire, England, Turing directed his faculties to code breaking. He was the mastermind behind the Turing Bombe, an electronic device designed to ascertain the continually changing settings of Germany's Enigma encryption machines. They could decrypt secret messages discovered, revealing critical military secrets.

"The scientific triumph at Bletchley - secret for the duration of the war and for 30 years after - had a greater effect on the outcome than even the Manhattan Project, the real bomb," wrote James Gleick in his 2011 book "The Information." "By the war's end, the Turing Bombes were deciphering thousands of military intercepts every day: processing information, that is, on a scale never before seen."

Designing computers

After the war, Turing went on to design pioneering computers and software at the National Physical Laboratory and the University of Manchester. In 1950, he wrote a seminal paper on thinking machines, or what would later be called artificial intelligence.

Turing famously predicted that by the end of the century, machines would be able to trick people into believing they were human almost a third of the time. Turing didn't exactly say that would mean machines were thinking, but suggested the distinction would largely cease to matter. At that point, humans would think of machines as thinking.

His prediction proved optimistic, but the "Turing test" became a sort of rallying point for artificial intelligence, driving the field forward. Conversation bots are evaluated each year against his benchmark at the Loebner Prize competition, as judges attempt to decipher man from machine in anonymous chats.

At the same time, computer scientists have hit upon better uses for the AI that Turing envisioned, by leveraging computing powers that supersede rather than mimic human abilities. Simultaneously translating across dozens of languages, for example, or sorting and searching the corpus of human knowledge.

'Indecency,' despair

Two years after Turing's landmark paper, he was arrested and prosecuted for acts of "gross indecency."

During an investigation into a robbery of Turing's home, the police realized he was having a sexual relationship with a man who was or knew the perpetrator. In lieu of prison, he was sentenced to undergo a course of estrogen treatments designed to "cure" him. The effect was chemical castration. It rendered him impotent. He gained weight and grew breasts.

"The little that was left of Alan Turing's life after his arrest was a slow, sad descent into grief and madness," Leavitt wrote.

In a letter to a friend, he worried his homosexuality would be directed against his controversial ideas, laying out his fears in the heartbreaking syllogism: "Turing believes machines think. Turing lies with men. Therefore machines cannot think."

In 1954, he bit into an apple poisoned with cyanide, in what came to be seen as an allusion to one of his favorite movies, "Snow White and the Seven Dwarfs." His death was ruled a suicide. But some family members, friends and observers, including Wolfram, have argued it was an accident.

The tragedy of his arrest and death were compounded as his contributions to computer science and top-secret war efforts were ignored or misattributed for years.

Britain's then-prime minister, Gordon Brown, issued an official apology to Turing in 2009. But in February, the British government once again denied petitions for a formal pardon, committing an act of gross indecency itself.

Conviction upheld

In dismissing the motion, Justice Minister Lord McNally said: "Alan Turing was properly convicted of what at the time was a criminal offense."

The scientific world, at least, has honored him with the redemption he deserves. The Turing Award, which Cerf won in 2004, is considered the highest honor in computer science. The field's practitioners have decreed 2012 the Alan Turing Year. And technologists, mathematicians and assorted academics have marked his 100th birthday with celebrations around the world.